1. Field of the Invention
The invention relates to a method for analyzing the effect of a gaseous medium on a biological test system using an extracellular metabolization system, and to a device for carrying out the method.
2. Description of the Related Art
Known in the art is to expose cellular test systems in the form of eukaryote cultures, in particular cell lines, primary cells, biopsies, lavages, isolates, PCLS and the like, to ex-vivo airborne substances of a native or artificial type so as to analyze the biological effect of these substances. The eukaryote cultures are here exposed to an artificial or natural test atmosphere, also referred to as exposition atmosphere.
Since the intermediate metabolic products of the specified airborne substances are often the first to become biologically active, a biological effect of the test atmosphere in the cellular test system only becomes detectable after having been able to form the specified intermediate metabolic products during a metabolization of the specified airborne substances.
Cited below are examples of cellular test systems in which an intracellular metabolization capacity was ruled out or confirmed:    (a) Isolates of primary cells with rather varyingly defined metabolizing capabilities/capacities that differ as a function of the respective isolation technique and isolation batch (e.g., hepatocytes of rat livers or from human biopsies; M. J. Gomez-Lechon et al., Hepatocytes—the choice to investigate drug metabolism and toxicity in man: Ir. vitro variability as a reflection of in vivo, Chemico-Biol. Int. (2006), dol: 10.1016/j.cbj.2006.19.013).    (b) Immortalized hepatocyte cell lines that can have a varying metabolizing capability/capacity depending on subpopulation (e.g., the human hepatoma cell line HepG2; Aden et al. 1979).    (c) Genetically altered cell systems (e.g., cell lines derived from V79 with defined expression of specific cytochrome P-450 forms; A. Townsend et al., Modeling the metabloc competency of gutathione S-transferases using genetically modified cell lines, Toxicology 181-182 (2002) 265-269; N. Krebsfaenger et al., V79 Chinese Hamster Cells Genetically for Polymorphic Cytochrome P450 2D6 and their Predictive Value for Humans, ALTEX 20, 3/03, 143-154).    (d) Cocultures of metabolically competent cells and non-metabolizing cells of the primary target tissue of the noxae (S. Bremer et al., Detection of the Embryotoxic Potential of Cyclophosamide by Using a Combined System of Metabolic Competent Cells and Embryonic Stem Cells, ATLA 30, 77-85, 2002).    (e) Tissue sections (D. S. Pushparajah et al., Evaluation of the precision-cut liver and lung slice systems for the study of induction of CYP1, epoxide hydrolase and glutathione S-transferase activities, Toxicology 231 (2007) 68-80).
The complexity of culture processes along with the availability and reproducibility of metabolization efficiency can be disadvantageous relative to these cellular test systems with intracellular metabolization systems.
The aforementioned cellular test systems with intracellular metabolization system also do not compulsorily satisfy the requirements imposed by various internationally test provisions, for example the “OECD Guideline for the Testing of Chemicals” No. 473, which mandate the presence of a sufficiently efficient metabolization system.
In order to satisfy these test requirements, it is known that use can be made of cellular test systems without intracellular metabolization or cellular test systems in which the efficiency of intracellular metabolization has not been verified, which are exposed in flat-bottomed culture flasks or round culture flasks, so-called roller bottles. The cellular test system is here coated with a mixture of conservation medium and an extracellular metabolization system, and the test atmosphere is continuously passed through the flask. In order to thoroughly mix the conservation medium, extracellular metabolization system and test atmosphere, the culture flasks are shaken, tilted or rotated.
The disadvantage to this method is that no direct and defined contact is possible between the test atmosphere and cellular test system. Therefore, the result is imbued with less sensitivity and specificity, as well as with the absence of an exact dosimetry.